Various types of battery jars have been known for many years and one exemplary example of one such industrial battery jar is set forth in my earlier U.S. Pat. No. 4,118,265. This patent relates to the fabrication of battery jars having elongated side and end walls, using an injection molding process in a way in which satisfactory dimensional control was obtainable by forming the jar from two independent sections. Subsequently those sections were then welded together to form a battery jar having opposing side and end walls, a closed bottom wall and an open top. The thickness of the side walls remained constant. The substance of U.S. Pat. No. 4,118,265 is hereby incorporated by reference.
At the present time, many motive power lead-acid battery cells are characterized by a flat-plate type construction technique. In this type of cell, it is necessary that the plates press snugly against each other to minimize the dropping of active material from them particularly when the battery is subjected to shock or vibration. This tight packing of plates also helps maintain battery performance. The length of each battery jar is determined according to the number of battery plates to be used. Once the battery elements are inserted within the jar the vertical load of those elements is supported on the bottom of the jar. The top of the side and end walls must also provide a suitable top surface which is sufficiently thick so that the top or cover of the battery jar can be heat-welded thereto with a strong and leak-proof joint.
I have now determined that it is possible to increase the electrical rating of a battery by employing additional quantities of battery acid within the battery case and at the same time substantially reduce the amount of plastic necessary to produce the battery jar walls and, in particular, by reducing the thickness of the side and end walls at least in the central portion of the battery jar or along a major portion of those side and end walls. These results are also accomplished without varying the outside dimensions of the battery jar. This process of increasing the electrical rating of the battery and reducing the amount of plastic must not decrease the precision required in forming the jar itself through injection molding techniques, and must continue to permit the development of an accurately dimensioned upper portion in order to provide the necessary cover-to-jar weld and the resulting joint. Additionally, bursting pressures of the battery jar must be maintained as it is not desirable to modify the side and end wall structure to the point that they will tear, crack or not be suitably weldable.